This project was initiated to study the role of catecholamines in the central and peripheral system in experimental and genetic hypertension and stress, and has now been extended to study the participation of other biogenic amines and estrogens in the central regulation of neurovegetative functions. Central catecholamines and histamine are involved in the regulation of all forms of hypertension studied, and in stress. Adrenaline is formed in brain by two enzymes with different localization and substrate specificity. Adrenaline may regulate noradrenaline metabolism in the pineal gland. There is a circadian rhythm for catecholamines in posterior pituitary. Estrogens modulate catecholamine and MAO activity in pituitary gland and brain stem. There are alterations in kidney levels of catecholamines and in alpha-receptor number in genetic hypertension. Genetically hypertensive rats also present alterations in heart catecholamines, in selective increases in catecholamine formation in the celiac and stellate ganglia.